A conventional system capable of using secondary battery packs connected in parallel has a configuration in which a diode is used for each battery pack to prevent backflow of electricity for parallel connection or a control signal is issued from a system main body so as to cause each battery pack to discharge its energy.
For example, PTL 1 (JP-A-2004-229391) discloses a battery pack having first and second battery blocks each in which a plurality of secondary batteries are connected in series and in parallel, one battery terminal to which one terminals of the first and second battery blocks are connected respectively via first and second switch means, the other battery terminal to which the other terminals of the first and second battery blocks are connected, a switch means for switching the first and second switch means when charging or discharging is carried out, a capacity detection means for detecting the capacity of each of the batteries in the first and second battery blocks, and a switch control means for controlling the switch means depending on the detected battery capacity, and when the first and second switch means are switched, after elapse of a predetermined time when one of the first and second switch means is turned OFF, the other switch means is turned ON.
[PTL 1] JP-A-2004-229391